Clutch



I. E. M WETHY Get. 5, 1954 CLUTCH 4 Sheets-Sheet 1 Filed Dec. 26, 1951 Oct. 5, 1954 l. E. MOWETHY 2,690,825

CLUTCH Filed Dec. 26, 1951 4 Sheets-Sheet 2 I. E. M WETHY Oct. 5, 1954 CLUTCH 4 Sheets-Sheet 3 Filed Dec. 26, 1951 I 1. mm 1 lwegy Oct. 5, 1954 Filed Dec. 26, 1951 l. E. M WETHY CLUTCH k 61 Mi 4 Sheets-Sheet 4 Patented Oct. 5, 1954 UNITED STATES- CLUTCH Irvin E. McWethy, Western Springs, 111., assignor to General Electric Company, a corporation of New York ATENT OFFICE 11 Claims.

This invention relates to improved clutch mechanisms.

It is an object of the invention to provide a clutch mechanism which will transmit substantially constant torque of predetermined value.

It is another object of the invention to provide power transmission means which has a maximum torque transmission limit to protect the drive motor against damaging overloads while the load is being accelerated.

It is a further object of the invention to provide an improved drive mechanism for rotating the spin tub of an extractor type clothes washing machine.

It is yet another object of the invention to provide an improved drive means for a domestic clothes Washing machine.

It is still another object of the invention to provide an improved mechanism for transferring motive power from the washing to the extraction devices of a clothes washing machine.

My invention is applicable to many types of machines in which the relatively heavy load is to be accelerated to high speed by motors of limited power. clothes washing machines of a type in which the clothes are washed, rinsed, and centrifugally dried in a single tub mounted for rotation about a vertical axis, may be operated by a one-quarter horsepower motor; and yet when the centrifugal extraction cycle begins, the total Weight of tub, Water, and clothing may be of the order of 225 pounds. This load is made increasingly burdensome by reason of the fact that the clothes load may be so eccentrically disposed within the tub as to impose a severely unbalanced condition during rotation. The motor load at the start of extraction is therefore heavy, and some washing machines provide for gradual acceleration by interposing fluid couplings between the motor and the spin shaft of the tub. Such couplings have been satisfactory in operation but are costly to manufacture, and having a factory-applied charge of oil or other transmission fluid are subject to leakage and resultant annoyance if the washing machine is carelessly or improperly handled in shipment.

Pursuant to the present invention, therefore, I eliminate the fluid drive and utilize a friction type clutch for transmitting motor torque to the spin shaft. By novel and mechanically simple mechanism, I provide a maximum torque transmission limit which protects the drive motor against damaging overloads.

The invention together with further objects For example, domestic electric and advantages thereof will best be understood by referance to the following specification, read in connection with the accompanying drawings, in which Fig. l is a fragmentary side sectional elevation of a washing machine embodying the invention; Fig. 2 is a fragmentary plan section taken on lines 2-2 of Fig. 1; Fig. 3 shows a typical agitator oscillating mechanism; Fig. 4 is a side sectional elevation showing one form of torquelimiting clutch; Fig. 5 is a plan section taken on lines 55 of Fig. 4; Fig. 6 is a plan section of the agitator jaw clutch taken on lines 6-6 of Fig. 4; Fig. 7 is a fragmentary side sectional elevation showing the relative position of operating clutch parts at the time of coupling the spin shaft to the driving sheave; Fig. 8 is an end elevation based on Fig. 7; Fig. 9 is a plan section taken on lines 99 of Fig. 7; Fig. 10 is a side sectional elevation of a second form of torque-limiting clutch, showing the same in spinshaft driving position; Fig. 11 is a plan section of the clutch of Fig. 10 taken on lines H--ll of said figure; Fig. 12 is a section taken through lZ-IZ of Fig. 10 showing the relationship between the cam sleeve and drive ring; Fig. 13 is a section taken through I3--l3 of Fig. 10 showing the drive flanges and its mechanical association with the spin shaft; Fig. 14 is a section taken through i l-44 of Fig. 10 showing the driving yoke; Fig. 15 is a side elevation taken in section on lines l5--l5 of Fig. 11 showing the cooperation of the respective camming means on the clutch disk and the cam sleeve; Figs. 16 and 17 are respeceively a top plan view and a side elevation of the clutch disk; and Fig. 18 is a portion of a motor amperage-time chart made during a test of a washing machine embodying the invention.

Referring now to Fig. 1, one form of clutch has been illustrated in application to a washing machine I having a suitable casing structure 2 within which is secured a water collector 3. Disposed within said water collector for rotation therein about a vertical axis is a tub 6 within which are placed the articles (not shown) to be washed. It will be understood that conventional means (not shown) are provided for filling the tub with the desired quantity of water or other suitable washing liquid and that under the control of a program switch the apparatus is conducted through a program including washing, rinsing, and centrifugal extraction cycles. Washing, for example, is accomplished by an agitator (not shown) fitted on the end of an oscillatable shaft 5; and centrifugal extraction occurs when the tub 4 is rapidly rotated by the cylindrical shaft 6 to which it is attached. During the centrifuging operation the agitator is disconnected from power and therefore is free to rotate with the tub. Such washing machines are well known; see for example that described in the Castner et al. U. S. Patent 2,513,844 granted July 4, 1950.

The drive mechanism supporting structure includes a rigid plate 1' carried by a substantially U-shaped yoke 3 flexibly supported by a channel member If! extending across the casing and suitably secured to the respective side walls at the base thereof. Specifically, within the central portion of the channel member, there is provided a short rubber mount l I having a threaded insert l2 which receives a bolt I l passing through a boss l5 at the center of yoke 8. It will be understood that the rubber mount may be bonded to the side walls of the channel member and that the boss [5 projects through a suitable opening in the web of the channel. Such a mounting is typical of many known in the art and provides for the gyration of the yoke and plate "5 about the mount H as a nodal point. Obviously, means must be provided to maintain the tub 4 in an upright position since it is supported primarily by the yoke 8. For this purpose there is provided a sleeve l6 having an upper ball thrust bearing ll and lower sleeve bearing [8 for journaling the spin shaft 6, and to the base of said sleeve is affixed a plate 23 from which extend the centering springs 2| adjustably anchored in brackets 22 welded on or otherwise secured to the casing 2. As best appears in Figs. 1 and 2, plate 26 is fixed to and supported above plate I by the spacers 23, which may be tubular posts adapted to receive bolts 25 passing through the respective plates 7 and 20. Sleeve it passes through a large opening 25 in the bottom of the water collector 3 and a flexible boot 26 seals against water leakage while permitting the sleeve freedom for oscillation during the centrifuging cycle,

A fractional horsepower drive motor 27 is secured to plate 1 with its shaft 28 vertical A sheave 3:! is connected by a belt 3| to a sheave 32 of an oscillating mechanism 33; and a sheave E l is connected by belt 35 to the spin shaft sheave 35. As best appears in Fig. 2, belt 35 also drives the sheave -37 of a pump 33 by which the water content of the water collector is removed. Water enters the pump through an outlet 40 at the bottom of collector 3 and a flexible inlet conduit ll leading therefrom. Discharge may be through a flexible conduit 42. 43 maintain tension in belts 3! and 35. Oscillation of agitate shaft 5 is accomplished by means of the conventional mechanism of Fig. 3 in which a pinion on shaft 44 driven by sheave 32 drives gear Q5. A crank arm 56 connects to the pivoted rack 47, which drives a pinion 48 freely rotatable on shaft 50. Said shaft is suitably secured within the frame of the agitate mechanism. Pinion 18 terminates in a jaw clutch component 5i having an axial socket 52 within which the lower end of agitate shaft 5 is journaled for rotation. The wall about said socket has upwardly facing drive grooves 53 arranged in cruciform pattern as indicated in Fig. 6.

As shown in Fig. 4, a clutch element 5 3 has a splined engagement with shaft 5 to permit free axial movement along said shaft. Said clutch element has diametrically opposed teeth 55 for engagement with one or the other of the sets of grooves 53. It is therefore obvious that with the Spring biased idler means clutch element in the Fig. 4 position the oscillation of shaft will be transmitted to shaft 5, whereas when it is raised along shaft 5 until teeth disengage from grooves 53, the driving connection between pinion t8 and shaft 5 is interrupted. As presently explained, the clutch element 54 carries a coupling device to establish a driving connection between sheave 3:2 and spin shaft 6. A convenient mechanism for shifting the clutch element may comprise a bell crank 56 pivotally mounted on plate '5. The forked arm 51 of said bell crank engages trunnions 58 of a shift yoke 60 which rides freely within a slot El provided in clutch element E l. Crank 56 is arranged to be rotated counterclockwise to the Fig. 4 position by means of the energization of a solenoid 62 having its plunger 63 connected to the leg 94 by a spring and when the solenoid is de-energized, it will be rotated clockwise by the reaction of spring which is anchored to plate I and to an ear El projecting upwardly from crank 56; said spring 66 is obviously placed under tension by the counterclockwise rotation of crank 55. The axial displacement of the clutch element B l for disconnecting shaft 5 from power operates to connect shaft 6 to power through the clutch mechanism comprising the present invention.

In Fig. 4 it appears that shaft 6 is freely rotatable relative to shaft 5, being supported with respect thereto on a thrust bearing 63 and snap ring 69, the latter being seated in a groove in shaft 6 asmis conventional. A sleeve hearing it] is interposed between shaft 6 and the hub H of sheave 32 and said sheave is therefore freely rotatable on the shaft. A drive block 72 is keyed to said shaft and means are provided to transmit power from said sheave to said block by a torque-limiting clutch assembly. The sheave 32 or its mechanical equivalent (for example, gear) is directly connected to the motor and will be considered to be the driving member for shaft 6.

In the specific embodiment shown in Fig. 4, sheave 32 has a drum portion 5 3 which provides a clutch element. The lower rim of said drum preferably has an inturned lip or flange for the support of the plurality of friction clocks i5. Said blocks are held in contact with drum !3 under substantial normal engagement pressure by a band it of spring material, preferably spring steel, to the radially outermost wall surface of which the friction blocks 75 are bonded or otherwise secured. As best appears in Fig. 5, the band, and associated friction blocks comp-rehend approximately 330 degrees of the full circumference of the drum. In a present embodiment of the invention, the free diameter of spring band 73 is of the order of 4 inches and when positioned within the drum 13, the diameter reduces to approximately 0% inches. It will thus be seen that the band is under appreciable. tension within the clutch drum. The height of the friction blocks 2'5 is inches. This arrangement has transmitted approximately 18- inch pounds of torque in actual test.

The friction block supporting band 16 is made a part of a power take-off means; a convenient arrangement is to bend one end of the spring band radially inwardly to form a driver 11. Power is transmitted from the driver 1'! to the drive block 12 by means of a coupling device 18 which rides freely within a slot 19 formed in the jaw clutch element 54. The coupling device has coupling members which may comprise the axially extending, diametrically opposed, plates 80, 80.! which have a sliding connection with drive block 12 by passage through the diametrically opposed slots 72.! thereof.

It will be recalled that shaft-driving member 32 is rotating so long as the motor is energized. The friction clutch assembly, including the power take-off finger H, is of course rotating with the sheave. When the jaw clutch element 54 is in the Fig. 4 position in which the inner shaft 6 is being oscillated, the driving sheave 32 rotates idly. To connect sheave 32 to shaft 6, the clutch element is raised (in an automatic washing machine this may be done by de-energizing solenoid 62 by operation of a cycle control switch, as is well understood) and coupling device 18 will rise, bringing its plates 80 and 80.l into the area circumscribed by the clutch drum 13. The upper corner of plate 80.! is cut away to the extent that the driver l7 will not engage it, whereas the upper corner of plate 80 is cut away only to the extent of requiring the clutch element 54 to be disengaged from the oscillator 5| before the plate 80 comes into the path of driver 1'! to form the positive drive link between driver I! and drive block H. The cut away portion of plate 80 provides a line contact at point of engagement. This is clearly indicated in Figs. '7 and 8. If at the time the clutch element 54 is elevated drive plate 80 is ahead of driver Ti, power transmission will, of course, not occur until the sheave completes the revolution to bring the elements 11 and 80 into engagement.

As a matter of practical operation, it is inevitable that the shaft 6 and its associated drive block 52 will lag behind sheave 32; for the sheave will have run free until the instant of engagement of the driver H with the plate 80 and the apparatus driven by shaft 8, having up to then been stationary, has substantial inertia. The substantial weight of the wash tub 4 and its contents has previously been noted, and in washing machine operation, the resistance to rotation of shaft 8 may be amplified by the eccentric position of masses of clothes within the tub and the gyratory action induced by such eccentricity as the tub accelerates.

The present invention prevents motor overloads during high-torque requirement periods by reducing the pressure of the friction blocks against the clutch element 13 if the torque increases beyond a designed limit. If because of excessive load on shaft 6 the shaft and its drive block if lag behind the sheave 32, the coupling device 18, which rotates at shaft speed because of its engagement with the drive block, will exert a force on power take-off device T! which in effect causes said device to rotate in an opposite direction relative to the sheave. The result is that commencing at the driver 71, the spring band l6 tries to wrap itself into a tighter coil, increasing the loading of the spring band, but decreasing the pressure of the friction blocks against the clutch drum l3. This permits the sheave to run more freely, and maintains a relatively constant load on the motor. As the inertia or other shaft load factors are overcome and the shaft speed increases, the spring band gradually restores the friction blocks to normal pressure and the shaft accelerates to eventual sheave speed.

A typical performance of the clutch disclosed in the foregoing embodiment is illustrated in Fig. 18, which is a reproduction of a recording ammeter chart showing the current drawn by the motor of a washing machine embodying the invention, during operation with a normal clothes load. The abscissae are minutes of time and the ordinates are amperes drawn by the motor. Reading from right to left, the portion from A to 13 represents the closing minutes of the Wash cycle in which the motor is driving the agitator shaft 5. At B the solenoid 62 has lifted clutch element 54 out of driven engagement with the oscillator 5|, and the plate has not yet engaged the driver 11. From B to C, therefore,-the motor is substantially running free. At C the sheave 32 has been connected to the drive block 12 by reason of the engagement of plate 80 and driver T1. The curve portion from C to D indicates the unloading of the motor by reason of the above-described clutch action, and D to E indicates the relatively constant motor load during the major portion of the spin cycle. The rise from E to F is indicative of the additional load imposed on the motor during a spray-rinse operation pursuant to which rinse water is sprayed against the clothing as the tub completes its final moments of spin. F to G represents the sprayrinse period and again indicates a relatively constant motor load. At G the motor circuit is interrupted and the motor is therefore no longer drawing current.

In the embodiment of Fig. 10 et seq., an axially operating disk type friction clutch element is employed instead of a radially applied band type clutch.

Sheave 8! has a fiat surface 8|.I providing a clutch element of substantial area. The sheave has a relatively heavy hub 82 riding on or having affixed thereto the sleeve bearing Ill for free rotation of said sheave on shaft 5. The friction member comprises a shallowly cupped clutch disk 83 faced with a ring, or ring segments, of friction material 84 and having a pluralityfor example, three-of sets of downwardly sloping cam surfaces 85, as best appears in Figs. 16 and 17. Power take-oir from sheave 8| comprises an assembly including the said cam surfaces of disk 83, an unloader cam '86, having a cylindrical body 81 rotatably carried on hub 82, and an upper rim or flange 88 formed with V-shaped cams 89 equal in number and arrangement to the sets of cams of disk 83. It also includes a driver member 9! freely rotatable about hub 82 and supported thereon by a thrust bearing 90 and snap ring 92. As best appears in Figs. 11 and 15, the body 81 fits freely within the central aperture of disk 83, with the cams 89 seated within cams 85. Cam body 8'! has diametrically opposed notches 37.1 at its base for the reception of lugs 93 projecting inwardly from the inner wall of the member Hi. The member 9! forms a base for a conical spring 94 which resiliently urges the friction disk assembly upward against clutch surface 8 l I.

Transmission of torque from sheave M to spin shaft 5 is accomplished by positioning certain coupling means between element 55 and the sheave power take-off assembly above described. Specifically, a mechanical connection is established from element 9| and a shaft driver ring 95 having keys 9K5 seated within slots in shaft 6, as best shown in Fig. 13. such mechanical connection results from the axial movement of a jaw clutch member 541, which is essentially similar to member 54 of the earlier embodiment. For example, teeth 55.! are provided for engagement with the notches 53 and the shift yoke 61] rides freely in groove ELI. A coupling device 91 has a cuplike hub portion freely supported on a jaw clutch member 54.] for rotation relative thereto, and has two diametrically opposed wings 98 to which are secured coupling elements 99 extending vertically in the plane of a diameter of shaft 5. As shown in Figs. 10, 12, and 13, elements 99 occupy slots 95A in ring 95 and may be projected into the path of rotation of lugs 9|.l of driver 9| when the jaw clutch member is raised to the Fig. 10 position. In other words, elements 99 always remain within the slots 95.! of ring 95, but are not engageable with the lugs 9H when the jaw clutch member 54.1 is dropped from the Fig. 10 position to one in which its jaws 55.l seat within the oscillator drive notches 53. It will be observed that the coupling device 91 is held on a bearing shoulder of clutch member 54.1 by a thrust bearing IEIEI and snap ring NH, and that drive ring 95 is supported on snap ring I02.

Assuming sheave 8| to be rotating, it will be obvious from the foregoing that clutch disk 83 will be rotating with it, for spring 94 holds the friction material 84 against the clutch portion 8L! of the sheave. The cam portions 85 of disk 83 are driving the unloader cam 86 by engagement with the cam portions 89 thereof. In turn, the unloader cam is rotating the member 9| by reason of the cooperating slot and tongue portions 81.! and 93. When coupling device 9! is elevated to the Fig. 10 position, the members 99 are engaged by the lugs 9|.I. Since said members are always in operative association with the ring 95, torque is immediately effective on said ring and applied thereby to shaft 6. It will be noted that here also the clutch member 54.!

disengages from oscillator 5| before members 99 come into driving relationship with member 9|.

If the load on shaft 6 is such as to cause the shaft to lag behind the sheave 8 las will almost inevitably be the case at the start of rotation of said shaftthe unloader cam '86 rotates relative to the clutch disk. The unloader cam is confined against axial movement, and the relative rotation of the clutch disk and unloader cam causes the cooperating unloader cam portions 89 and clutch disk cam portions 85 to drive relation to the drive radius, the maximum torque transmitted to the shaft 6 in the instant embodiment is established by the angle of cams 89 and the pressure of spring 94.

While there has been described what is at pres.- ent considered to be the preferred embodiments of the invention, it will be understood that various modifications may be made therein, and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.

I claim:

1. A mechanism for connecting a rotatable shaft to a driving member freely rotatable on said shaft and deriving power from a drive motor, said driving member having means providing a clutch element; comprising friction blocks disposed about said clutch element for engagement therewith, spring means for urging said friction blocks into such engagement, power take-off means operatively associated with said spring means and effective upon rotation in one direction relative to said shaft to tension said spring means for reduction of the pressure exerted by said blocks against said clutch element, a drive block fixed to said shaft, a coupling device axially movable on said shaft, coupling means carried by said device for establishing a driving connection between said power take-01f and said drive block, said coupling means being rotated at shaft speed by said drive block and urging said power take-01f means into said one direction of rotation when the shaft is rotating at less than the speed of said driving member, and means for axially moving said coupling device optionally into or out of operating position relative to said power take-off means.

2. A mechanism for connecting a rotatable shaft to a driving sheave freely rotatable on said shaft and deriving power from a drive motor, said sheave having wall means defining a clutch element; comprising friction means disposed about said clutch element for engagement therewith, a carrier for said friction means, means for biasing said carrier toward said clutch element to urge the friction means into pressure engagement therewith, a rigid member extending from said carrier and effective upon displacement in one direction relative to said driving sheave clutch element to alter the bias on said carrier for reduction in the pressure of engagement of said friction means and said clutch element, a coupling device axially movable on said shaft, a drive block fixed to said shaft intermediate the coupling device and said rigid member, rigid coupling means on said device in permanent sliding engagement within said drive block whereby said coupling means is rotatable at shaft speed, and means for shifting said coupling device on said shaft to bring the coupling means thereof into torque-transmitting association with said rigid member; said coupling means influencing said member into displacement in said one direction when said drive block is rotating at less than the speed of the driving sheave.

3. A mechanism for connecting a rotatable shaft to a driving member freely rotatable on said shaft and deriving power from a drive motor, said driving member having means providing a clutch element; comprising friction members disposed about said clutch eler.ent for engagement therewith, spring means for urging said friction members into such engagement, a power take-off operatively associated th said spring means and effective upon rotation in one direction relative to said driving member to bias said spring means for reduction of the pressure exerted by said friction members against said clutch element, a drive block fixed to said shaft, a coupling device axially movable on said shaf t, coupling means carried by said device in continuous slidable engagement with said drive block for establishing a driving connection between said power take-off and said drive block, said coupling means being rotated at shaft speed by said drive block and urging said power take-oil into said one direction of rotation when the shaft is rotating at less than the speed of said driving memher, and means for axially moving said coupling device optionally into or out of operating position relative to said power take-off.

4. A mechanism for connecting a rotatable shaft to a driving sheave freely rotatable on said shaft and arranged to be connected toe drive motor, said sheave having a concentric cavity of which wall portions provide a clutch element; comprising friction members disposed within said.

cavity for engagement with said wall portions, spring means for urging said friction members into such engagement and being rotated thereby with said sheave, a power take-off including an element of said spring means and effective upon rotation in one direction relative to said sheave to bias said spring means for reduction of the pressure exerted by said friction members against said clutch element, a drive block fixed to said shaft, a coupling device axially movable on said shaft, rigid coupling means carried by said device and in continuous sliding engagement with said drive block, said coupling means being movable into the path of rotation of said spring means element to establish a driving connection between said power take-01f and said drive block, said coupling means being rotated at shaft speed by said drive block and urging said power takeoff into said one direction of rotation when the shaft is rotating at less than the speed of said sheave, and means for axially moving said coupling device optionally into or out of operating position relative to said power take-off.

5. A mechanism for connecting a rotatable shaft to a driving sheave freely rotatable on said shaft and deriving power from a drive motor, said driving sheave having peripheral wall means providing a clutch element; comprising a plurality of friction blocks disposed about said wall for engagement therewith, a strip of springable material secured to said blocks, said strip biasing said blocks into pressure engagement with said wall, a member extending radially from said springable strip and effective upon displacement in one direction relative to said driving sheave element to reduce the pressure of engagement of said friction blocks and said peripheral wall, a coupling device axially movable on said shaft, a drive block fixed to said shaft intermediate the coupling device and said rigid member, rigid coupling means on said device slidably extending through said drive block whereby said coupling means rotates at shaft speed, and means for shifting said coupling device on said shaft to bring the coupling means thereof into power-transmitting engagement with said radially extending member; said coupling means exerting pressure on said member for displacement in said one direction when said drive block is rotating at less than the speed of the driving sheave.

6. A mechanism for connecting a rotatable shaft to a driving sheave freely rotatable on said shaft and deriving power from a drive motor, said driving sheave having peripheral wall means providing a clutch element; comprising a plurality of friction blocks disposed about said wall for engagement therewith, a strip of spring able metal secured to said blocks and biasing the same into pressure engagement with said wall, a rigid member extending radially from one end of said strip and effective upon displacement in one direction relative to said driving sheave to reduce the pressure of engagement of said friction blocks and said wall, a coupling device axially movable on said shaft, a drive block fixed to said shaft intermediate the coupling device and said rigid member, rigid coupling means on said device in permanent sliding engagement within said drive block whereby said coupling means rotates at shaft speed, and means for shifting said coupling device on said shaft to bring the coupling means thereof into powertransmitting engagement with said rigid memher; said coupling means exerting pressure on said member for displacement in said one direc- 10 tion when said drive block is rotating at less than the speed of the driving sheave.

7. In combination, a shaft mounted for rotation, a clutch element mounted on shaft for free rotation thereon, means for driving said clutch element, a cooperating clutch structure disposed about said shaft and including friction means and radially expansible spring means secured thereto, said spring means urging said friction means into pressure engagement with said clutch element, a rigid extension projecting radially toward said shaft from an end of said spring means, a drive block fixed to said shaft, and rigid power transmission means operatively associated with said drive block for rotation therewith and movable into the path of rotation of said rigid extension whereby the latter may rotate said drive block and shaft; said power transmission means operating to displace at least a portion of said spring means in a direction away from said clutch element in the circumstance that said drive block and associated shaft are rotating at a less speed than said clutch element.

8. In combination, a shaft mounted for rotation, a clutch element mounted on said shaft for free rotation thereon, means for driving said clutch element, a cooperating clutch structure disposed about said shaft and including friction means and radially expansible spring means secured thereto, said spring means urging said friction means into pressure engagement with said clutch element, a rigid extension projecting radially toward said shaft from an end of said spring means, a drive block fixed to said shaft, rigid power transmission means slidably associated with said drive block for rotation therewith and movable into the path of rotation of said rigid extension whereby the latter may rotate said drive block and shaft, and means for moving said power transmission means into or out of said path of rotation; said power transmission means operating to displace at least a portion of said spring means in a direction away from said clutch element in the circumstance that said drive block and associated shaft are rotating at a less speed than said clutch element.

9. In combination, a shaft mounted for rotation, a clutch element mounted on said shaft for free rotation thereon, means for driving said clutch element, a cooperating clutch structure disposed about said shaft and including friction blocks and a clutch disk supporting the same, spring means engaging with said clutch disk to urge said friction blocks into pressure engagement with said clutch element, cam members on said clutch disk, an unloader cam rotatable relative to said disk and having cam means engaging with said clutch disk cam members for torque transmission therebetween, a drive block fixed on said shaft, and means for transmitting torque from said clutch disk through said unloader cam to said drive block; the unloader cam and said clutch disk cam elements cooperating to urge said clutch disk away from said clutch element in the circumstances of relative rotation of said clutch disk and unloader cam.

10. In combination, a shaft mounted for rotation, a clutch element mounted on said shaft for free rotation thereon, means for driving said clutch element, a cooperating clutch structure disposed about said shaft and including friction blocks and a clutch disk supporting the same, spring means engaging with said clutch disk to urge said friction blocks into pressure engagement with said clutch element, cam members on said clutch disk, an unloader cam disposed about said shaft for rotation relative thereto and having cam means engaging with said clutch disk cam members for torque transmission therebetween, means for confining said unloader cam against axial movement, a drive block fixed on said shaft, and means for transmitting torque from said clutch disk through said unloader cam to said drive block; the unloader cam and said clutch disk cam elements cooperating to urge said clutch disk away from said clutch element in the circumstances of relative rotation of said clutch disk and unloader cam.

11. In combination, a shaft mounted for rotation, a clutch element mounted on said shaft for free rotation thereon, means for driving said clutch element, a cooperating clutch structure disposed about said shaft and including friction blocks and a clutch disk supporting the same, spring means engaging with said clutch disk to urge said friction blocks into pressure engagement with said clutch element, cam members on said clutch disk, an unloader cam disposed about said shaft for rotation relative thereto, said unloader cam having cam means overlying said clutch disk cam members in engagement therewith for torque transmission therebetween, means for confining said unloader cam against axial movement, rigid means extending radially from said unloader cam in non-rotatable association therewith, a drive block fixed on said shaft, and coupling means for mechanically interconnecting said radially extending means and said drive block to transmit torque therebetween; the unloader cam and said clutch disk cam elements cooperating to urge said clutch disk away from said clutch element in the circumstances of relative rotation of said clutch disk and unloader cam.

References Cited in the file of this patent 

